Background: After acute myocardial infarction the preservation of the microvasculature is a pre-requisite for myocardial viability, limited ventricular remodeling and a better prognosis. Intracoronary myocardial contrast echocardiography after acute myocardial infarction can detect the extent of microvascular damage. We hypothesized that intravenous myocardial contrast echocardiography after acute myocardial infarction treated with primary coronary angioplasty can predict the contractile reserve at low-dose dobutamine echocardiography, myocardial functional recovery and left ventricular remodeling.
Methods: We studied 37 patients with a first acute myocardial infarction and submitted to primary coronary angioplasty. All patients underwent echocardiography on the day they had the acute myocardial infarction, intravenous myocardial contrast echocardiography with power Doppler imaging 2.9 +/- 0.5 days later and dobutamine echocardiography 3.7 +/- 1.2 days after the acute myocardial infarction. In all cases, an echocardiography was performed at 3 months of follow-up.
Results: At intravenous myocardial contrast echocardiography, 25 patients showed contrast enhancement (reflow) and 12 a sizeable contrast defect (no-reflow). Reflow patients were found to have a regional wall motion score index similar to that of the no-reflow patients on the first day echocardiogram (2.6 +/- 0.4 vs 2.8 +/- 0.2, p = NS), but this parameter was smaller than that of the no-reflow patients at dobutamine echocardiography (1.5 +/- 0.4 vs 2.6 +/- 0.2, p < 0.0001) and at follow-up echocardiography (1.5 +/- 0.5 vs 2.6 +/- 0.2, p < 0.0001). The sensitivity and specificity of intravenous myocardial contrast echocardiography in identifying myocardial functional recovery at follow-up were 80 and 64%, while the sensitivity and specificity of dobutamine echocardiography were 85 and 76%. In no-reflow patients the left ventricular volumes increased from the acute to the chronic phase (end-diastolic volume from 71.9 +/- 14.1 to 100.9 +/- 40.6 ml/m2, p < 0.0001, +28%; end-systolic volume from 43.1 +/- 10.1 to 61.1 +/- 30.1 ml/m2, p < 0.0001, +29%), while they remained constant in reflow patients (end-diastolic volume from 71.8 +/- 20.1 to 71.1 +/- 15.4 ml/m2, p = NS, -1%; and end-systolic volume from 39.9 +/- 11.9 to 36.3 +/- 12.8 ml/m2, p = NS, -8%).
Conclusions: Intravenous myocardial contrast echocardiography is capable of identifying patients with a post-infarction contractile reserve and myocardial functional recovery; it also allows the early identification of patients prone to late left ventricular dilation, thus permitting a more aggressive diagnostic and therapeutic strategy.